Multipurpose direct current relay

ABSTRACT

THE RELAY HAS A CONTACT-OPERATING ARM ASSEMBLY INCLUDING AN ARAMTURE AND AN ADJUSTABLE RETAINING MEANS WHICH RETAINS THE ARAMATURE IN PIVOTAL RELATIONSHIP WITH A MAGNETIZABLE FRAME. THE RETAINING MEANS PERMITS THE CONTACT ARM ASSEMBLY TO BE REMOVED FROM THE FRAME FOR FULL ACCESS TO AN OPERATING COIL OR COILS WITHOUT THE USE OF A TOOL. PROVISION IS MADE FOR READY INTERCHANGE OF DIFFERENT   CONTACT MAKING AND BREAKING DEVICES AND DIFFERENT OPERATING COILS SO THAT THE RELAY CAN BE USED FOR A WIDE VARIETY OF CIRCUIT CONTROLLING FUNCTIONS.

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I MuL'rIruBPdsE DIRECT. CURRENT RELAY Fi led Feb. 25, 1969 1 s Sheets-Sheet 2 INVEN TORS. DAVID L. SW/NDL ER DE/V/V/S J. OBLAK CHARLES ALLAN .SCHURR Feb. 16, 1971 D. L. SWINDLER ETAL 3,564,467

MULTIPURPOSE DIRECT CURRENT RELAY Filed Feb. 25, 1969 5 Sheets-Sheet 4 lNVE/VTORS Fgb. 16, 1971 1 D, L, SW NDLER ETAL 3,564,467 MULTIPURPOSE D-IRECT CURRENT RELAY -s She-ets-Shet 5 Filed Feb. 25, 1969 f6 lO/bk I JIM llviAflua AI... H 0 7m [AH mH' w 0- amw (0 5 Q a, a & mU WH Harm, 455p R 5 7 mxx H N D A N NL NU NMW f /s m- QJ S L E wmfl Wm? 0 0 0 W M United States Patent 3,564,467 MULTIPURPOSE DIRECT CURRENT RELAY David L. Swindler, Northfield, Dennis J. Oblak, Seven Hills, and Charles Allan Schurr, Shaker Heights, Ohio,

assignors to Square D Company, Park Ridge, 11]., a

corporation of Michigan Filed Feb. 25, 1969, Ser. No. 802,004 Int. Cl. H01h 50/16 US. Cl. 335132 16 Claims ABSTRACT OF THE DISCLOSURE This invention relates to electromagnetic relays, and more particularly to a clapper-type direct-current relay, the armature of which is biased toward one position and electromagnetically moved to another position, with contacts of the relay being operated upon movement of the armature between the two positions.

Electromagnetic relays have a broad range of applications in electrical circuitry as pilot switching devices for controlling contactors, solenoids, electromagnetic brakes, and other electrical equipment in industrial process control systems, electric motor control systems, and the like. Because of the resulting multiplicity of circuit-controlling characteristics which such relays are called upon to provide for these various applications, a considerable variety of relays has been developed and is now being used.

One well-known type of direct-current relay comprises an electromechanical operating mechanism together with one or more contact making and breaking devices of relatively low power rating. The contact devices of such relays are commonly of modular construction to facilitate repair and replacement and to permit a selected number of contact poles to be operated by a single electromagnetic operator. Another type of relay, known as a plugging relay, is used as a definite purpose relay in motor control systems to control the application of power to the motor during sudden reversals of the motor. Such applications require a relay having accurate pickup and drop-out characteristics and, for this reason, plugging relays have been of a different design than relays used for general purposes. Still other designs of definite purpose relays are used to provide under-voltage protection in electrical control circuits, and to control acceleration and deceleration of adjustable speed shunt motors by control of the motor field windings.

While the foregoing discussion of the different types and purposes of relays is by no means all inclusive, it serves to illustrate the demands upon manufacturers of electrical control equipment to produce and stock many relays, each of which is different in construction and employs different components. Consequently, any reduction in the number of different components and in the variety of separate relays required to achieve different control functions is of benefit to manufacturers and users alike.

The present invention achieves this desired result in that the basic relay can be altered to suit a variety of different purposes by selective assembly of the relay from but a small number of components. For example, the present ice relay can be provided, as desired, with one through four identical double-pole modular contact units thereby to provide up to eight switching circuits. Additionally, for switching inductive circuits, a contact assembly incorporating a magnetic blowout can be substituted for the modular contact units. Further, for field acceleration or deceleration control which requires special operating coil configurations, a novel two-piece terminal block is provided to facilitate assembly.

One feature of the present relay which contributes substantially to the ease of interchangeability of components resides in the manner in which the contact-operating arm assembly is retained in pivotal relationship with respect to the magnet frame. The armature of the assembly is pivotally supported in a knife-edge bearing on the frame by a spring-biased adjustable retaining means which permits the contact-operating arm assembly to be removed from the frame without the use of a tool.

Accordingly, a principal object of the present invention is to provide an electromagnetically-operated clapper-type relay which may be assembled, selectively, to accomplish a relatively large variety of circuit-controlling functions from but a relatively small number of interchangeable components.

Another object is to provide an electromagneticallyoperated clapper-type relay in which the contact-operating arm assembly is readily removable from the relay frame without the use of tools.

Still another object is to provide an electromagnetic relay having an improved contact mounting configuration whereby a variety of interchangeable circuit making and breaking devices of different power ratings may be provided and one or more selected for operation by a common contact-operating arm.

Other objects and advantages of this invention will become apparent from the following specification wherein reference is made to the drawings, in which:

FIG. 1 is a perspective view of an electromagnetic relay in accordance with this invention, two modular contact units being provided to perform the circuit making and breaking function of the relay;

FIG. 2 is a front view of the relay of FIG. 1 showing the relay with four modular contact units instead of two;

FIG. 3 is a side view of the relay as in FIG. 2, the relay being in its energized position;

FIG. 4 is an exploded perspective view of the relay of FIG. 1, and, in addition, shows the major component groups from which may be selected individual components for assembling the relay for different purposes;

FIG. 5 is a perspective view similar to that of FIG. 1, but with the relay assembled to include a high interrupt ing capacity contact assembly in place of the modular contact units of FIG. 1 and to include a modified operating coil and terminal structure;

FIG. 6 is a bottom view of two terminal supports of the terminal structure illustrated in FIG. 5, showing the terminal supports disposed in one positional relationship with respect to each other;

FIG. 7 is a bottom view of the terminal supports of FIG. 6, but with the terminal supports disposed in a different positional relationship with respect to each other; and

FIG. 8 is a perspective view of a portion of the relay of this invention showing how the contact assembly of FIG. 5 may be modified, in connection with a re-arrangement of the contact structure carried by an operating arm of the relay, for use as a normally-closed circuit making and breaking device.

Referring to FIG. 1, an electromagnetic relay in accordance with this invention comprises a base 10 having upper and lower offset flange portions and having means such as upper and lower mounting slots 10a and 10b,

respectively, by which the relay may be mounted upon a control panel. As illustrated, the mounting slot a is formed in key-hole fashion and the mounting slot 10b is open at its lower end to facilitate installation over mounting studs or the like. Preferably the base 10 is formed of sheet steel and may be embossed to provide a pair of shallow ribs 11 for additional rigidity.

As best illustrated in FIGS. 3 and 4, a magnet frame 12 having two portions 12a and 12b disposed generally at right angles to each other is secured to the base 10, together with a cylindrical core 14, by a screw 15 which passes through aligned openings in the base and the frame portion 12a and is received in a threaded axial socket in the core. A plurality of bosses 16 formed on the base 10 are located so that a pair is disposed at each side of the frame portion 12a, thereby to constrain the frame 12 in proper alignment with respect to the base 10; likewise, a roll pin 17 (FIG. 3), received in aligned openings in the core 14 and the frame portion 12a, prevents rotation of the core relative to the frame 12.

A coil 18 comprising a winding encapsulated in an insulating material, such as epoxy or the like, and having an axial opening extending therethrough is received on the core 14 and is retained in place by a core cap 19 secured to the outer end face of the core 14 by a screw 20. A spring washer 21, disposed between the coil 18 and the frame portion 12a, urges the coil 18 firmly against the core cap 19. The coil 18 is provided with a pair of terminals 22 facilitating connection of the coil to a source of power and, in addition, the coil 18 includes a locating protrusion 18a extending radially from the body of the coil and having a flat surface which cooperates with the underside of the frame portion 12b to prevent rotation of the coil and to assure proper orientation of the terminals 22 with respect to the remainder of the relay.

As shown in FIGS. l-4, an operating arm assembly 24 comprising an armature 25, an operating arm 26, and a spring-biased retaining means 27 is mounted on the frame portion 12b for to-and-fro pivotal movement. The armature 25 is a fiat, generally rectangular steel plate member and is secured to the operating arm 26 by a screw 29 extending through a suitable opening in the arm 26 and threaded into a hole in the armature. Although only one is shown, a pair of horizontally-spaced rearwardly-facing projections 30 (FIG. 3) on the operating arm 26 are received in complementary aligned openings in the armature 25 and assist in maintaining the armature in proper position on the operating arm. Preferably, the operating arm 26, including the projections 30, is molded of a strong, electrically-insulative material such as glass-reinforced polyester.

As previously mentioned, an important feature of this invention resides in that the operating arm assembly 24 may be easily removed as a single integral unit from the relay without use of a tool. The structure for accomplishing this function will now be described.

As best illustrated in FIG. 3, the frameportion 12b near its free end has a generally V-shaped groove or notch 31 formed in its underside which receives a bevelededge portion 32 of the armature 25. The armature 25 is urged upwardly into knife-edge bearing relationship in the notch 31 by the spring-biased retaining means 27 which includes a helical spring 34 and a securing means 35 threaded on a spring-adjusting rod 36 which is threaded at its upper end portion and has a spring-retaining seat 37 secured to its lower end portion. The upper end portion of the rod 36 is received loosely in a slot 120 (FIGS. 1 and 4) formed in the frame portion 12b. The spring 34 is dis posed about the rod 36 within a rectangular cavity 38 formed in the operating arm 26 and is seated at its lower end on the retaining seat 37. The upper end of the spring 34 bears against an upper wall of the cavity 38. The rod 36 and seat 37 are free to move vertically within the confines of the cavity 38.

The securing means 35 comprises an adjusting nut 39 and a seating washer 40 which is retained on the nut 39 by an upset portion thereof, but which is free to rotate relative thereto. As illustrated in FIGS. 1 through 3, the washer 40 has a pair of bent-over downwardly-directed pointed portions 40a which seat in a pair of relatively shallow notches formed in the upper surface of the frame portion 12b on opposite sides of the slot 120. If desired, a lock nut 42 may be provided to maintain the adjusting nut 39 in adjusted position on the rod 36.

The spring 34 urges the operating arm 26 and the securing means 35 toward each other. Thus, the seating washer 40 of the securing means 35 is urged into seating engagement with, and the beveled edge portion 32 of armature 25 is urged into knife-edge bearing relationship with, the frame portion 12b thereby to retain the operat-' ing arm assembly 24 in pivotal relationship with the frame 12. y

In addition to its function'of assisting in retaining the operating arm assembly in pivotal engagement with the frame 12, the spring 34 also biases the operating arm 26 so as to urge it and the armature 25 to swing in a direction away from the core 14. The manner in which this is accomplished is best illustrated in FIG. 3. Referring to FIG. 3, it will be observed that the line of action of the spring 34 does not pass through the fulcrum formed by the knife-edged pivotal connection between the armature 25 and the frame portion 12b, but instead lies a measurable distance forwardly therefrom. Thus the spring 34 provides a moment of force tending to urge the operating arm 26 and the armature 25 counterclockwise (as viewed in FIG. 3) about the knifeedged pivotal connection. As is further evident from FIG. 3, the position of the nut 39 may be adjusted on the shaft 36 so as to alter the extent of compression of the spring 34, whereby the spring force biasing the operating arm assembly 24 to its open position away from the core 14 may be selectively determined. Because the washer 40 is free to rotate relative to the adjusting nut 39, such adjustment of the spring force may be effected without disturbing the seating engagement of the securing means 35 with the frame portion 12b.

A stop means for determining the open position of the operating arm assembly 24 comprises an adjustable nut 44 threaded on a stud 45 fixed to, and extending normal to, the base 10. In the open position, a raised boss on a shoulder 46 positioned adjacent the lower portion of an opening 47 in the operating arm 26 engages the inner face of the nut 44 thereby to prevent further movement of the operating arm assembly 24 in a direction away from the core 14.

Removal of the operating arm assembly 24 from the magnet frame 12 may be accomplished merely by physically drawing the securing means 35 out of seating engagement with the frame portion 12b and, at the same time, removing the armature 25 from the notch 31. As mentioned, this can be accomplished without the use of a tool of any sort by virtue of the spring-biased retaining means 27. The shaft 36 of the spring-biased retaining mean may then be withdrawn from the frame portion 12b by way of the slot 12c (FIGS. 1 and 4) which is open forwardly of the frame portion 12b for that purpose. The opening 47 in the operating arm 26 is sized so as to permit passage of the nut 44 therethrough for removal of the operating arm assembly 24.

Referring now to FIG. 4, a variety of interchangeable circuit making and breaking devices or components of different power ratings may be employed to perform the electrical switching function of the relay. In a configuration suited for general purpose use, and many definite purpose uses, the relay may be provided with contact means comprising, selectively, from one through four identical modular contact units such as the units 50. The internal structural details of the contact unit 50 are not important for the purposes of this disclosure, it being apparent that any appropriately sized single or double pole switch provided with a self-restoring reciprocable contact operator such as the push button 51 may be employed in the present structure. The contact units 50 are mounted, either in pairs as illustrated in FIG. 4, or singly, on a mounting bracket 52, and either one or two of the mounting brackets may be fastened to the base 10, each by a pair of screws 52a.

FIG. 1 illustrates the manner of mounting one of the brackets 52 to the base of the relay when it is desired to provide only a pair of the contact units for operation by the operating arm 26. As shown in FIG. 1, the push buttons 51 are operated, consequent upon to-andfro pivotal movement of the operating arm 26, by direct engagement with a lower end portion of the arm 26. Although two of the modular contact units 50 are provided in the embodiment of FIG. 1, it will be apparent that only a single contact unit 50 may be mounted to the bracket 52 if desired.

In FIG. 2 there is illustrated the manner of mounting two of the brackets 52 to the base 10 of the relay, each bracket 52 carrying two of the modular contact units 50. This mounting configuration is especially adapted for enabling either three or four of the contact units 50 to be operated by the operating arm 26. For this purpose, the operating arm 26 is provided with a pair of extension arms 54 (FIGS. 2, 3, and 4) which are received on opposite sides of a lower end portion of the operating arm 26 and are secured to the arm 26 by a conventional screw and nut fastener 55. As best depicted in FIG. 1, the lower portion of the operating arm 26 has a generally rectan gular shaped opening 56 through which the screw fastener passes, and on each side of the arm 26 there is also a shallow rectangular recess 57 for assuring proper positioning of the extension arms 54.

When the relay is to be used for switching highly inductive circuits, a stationary contact assembly 59, best illustrated in FIGS. 4 and 5, may be substituted for the modular contact units 50 and their associated mounting brackets 52. The stationary contact assembly 59 is like that disclosed in co-pending application Ser. No. 791,951, filed Jan. 17, 1969, and comprises an insulating contact block 60 molded of hard and dense insulating material and having a pair of recesses 61 and 62 in opposite sides of a front portion of the block and which define an intermediate web portion 64 and respective overhanging upper wall portions 65 and 66.

The stationary contact assembly 59 also includes a pair of identical contact arms 71. Each of the contact arms 71 has a straight intermediate portion 72 with an inwardlyturned contact-carrying portion 74 at one end. At the other end of the intermediate portion 72, each contact arm 71 has a Z-shaped portion including an ouwardlyturned mounting portion 75 and an outwardly-turned terminal portion 76. Each portion 74 carries a stationary contact 78, and each portion 76 has a U-shaped wire clamp or terminal 79 secured thereto. Centrally of each intermediate portion 72 is an inwardly-directed protuberance 80 and centrally of each portion 75 is a hole receiving a screw 81 (FIG. 8).

For controlling arcs formed at the contacts 78, the contact assembly 59 includes a pair of identical disk-shaped circular permanent magnets 82, the opposite side faces of each of which are of opposite polarity. The magnets 82 are formed preferably of a rubber-bonded barium ferrite composition, and each has a cylindrical axial recess at least on one side. Snugly received about the periphery of each magnet 82 is a split rim '84 made of non-flux-conducting metal having good arc-resistant properties such as copper, a copper alloy, or aluminum. The rims 84 have a normal inner diameter less than the diameter of the magnets 82 and are resilient so as to be frictionally held in position when assembled on the respective magnets 82.

The assembled magnets 82 and rims 84 are placed in the respective recesses 61 and 62 with the rims 84 bearing against respective front-facing semicircular locating surfaces (not visible in the drawings). Preferably, the outer side surfaces of the magnets 82 are at an angle of ninety degrees with respect to front-facing flat surfaces 85 of the respective recesses 61 and 62 and the portion 72 of each contact arm 71 before assembly is at an internal angle of more than ninety degrees with respect to the mounting portion 75. Thus, when the contact arms 71 are secured to the contact block 60 by the screws 81 nuts being tightened on the rear ends of the screws, the resiliency of the contact arms 71, and reception of the protuberances 80 into the respective openings in the magnets 82 maintain the respective magnets 82 in position and insure that there is a good electrical connection between the contact arms 71 and the respective rims 84.

The contact assembly may be mounted on the base 10 by a pair of screws (not shown) which are recessed in respective openings 86 (only one of which is shown).

For cooperation with the stationary contacts 78, a. contact bridge 87 is received in the opening 56 of the operating arm 26 and is spring-biased toward the stationary contacts 78 by a helical spring 88 retained by a retainer 89. To-and-fro rocking action of the operating arm assembly 24 causes engagement and disengagement of the contact bridge 87 with respect to the stationary contacts 78.

The normally-open relay of FIG. 5 may be converted to a normally-closed relay as shown in FIG. 8 by substituting, for the contact arms 71, longer contact arms 90 having inwardly turned portions 91 carrying respective contacts 92. The positions of the contact bridge 87, spring 88, and retainer 89, are reversed from the positions shown in FIG. 5 so that the contacts 92 are engaged by the contact bridge 87 when the operating arm assembly 24 is in its unattracted position.

The flexibility of the relay of this invention is further illustrated in FIG. 5 which shows one example of how different coil arrangements can be provided. Relays for controlling direct-current shunt motors often require that the relay contacts be responsive to a fixed magnetic field and a magnetic field related to the current in the motor armature. To this end, such relays require both a shunt coil and a series coil. In FIG. 5, a shunt coil 94 similar to but shorter than the coil 18 is received on the core 14 adjacent the frame portion 12m and a series coil 95 formed of heavy copper strap is also received on the core 14. The coil 94 has a pair of terminals 96 (only one of which is shown) and the coil 95 has two tangentially-extending terminal arms 98 and 99 fastened at their outer end portions by respective screws 100 to respective identical terminal supports or insulators 101 and 102 which facilitate connection of the coil 95 to a source of power. The insulators 101 and 102 are secured to the frame 12 by a pair of screws 103 (only one of which is shown) received in threaded mounting holes in the frame portion 12b. The screws 100 receive respective wire clamps 104 for facilitating the connection of wires (not shown) from the source of power to the terminal arms 98 and 99.

Because series coils such as the coil 95 may be of different sizes so that the terminal arms 98 and 99 are different distances apart, provision is made to mount the insulators 101 and 102 in two different positions with respect to each other as shown in FIGS. 6 and 7. To this end, the insulator 101 has a pair of slots 101a and 101b on opposite sides of a projecting tab 101a and the insulator 102 has a pair of slots 102a and 102b on opposite sides of a tab 1020.

When a relatively small series coil is to be used as the coil 95, the insulators 101 and 102 are arranged as shown in FIG. 6 with the tabs 101a and 1020 received in the slots 102a and 101a, respectively. When a larger series coil is required, the insulators 101 and 102 are arranged as shown in FIG. 7 with the tabs 101a and 1020 received in the slots 102b and 101b, respectively.

Each insulator 101 and 102 has a pair of spaced openings 105 adapted to receive screws for mounting the insulators to the relay frame 12. As is evident from an inspection of FIGS. 6 and 7, the openings 105 are so spaced on each insulator as to permit the pair of insulators 101 and 102 to be selectively mounted in either of the positions illustrated by a single pair of screws received in but a single pair of threaded mounting holes in the frame 12.

We claim:

1. A multipurpose clapper-type D-C relay comprising a magnetic frame including a portion having oppositely facing parallel surfaces, a flux-conductive core in fluxconducting relation at one of its end portions with the frame, a coil surrounding the core, means facilitating connection of the coil to a source of control power, a movable operating arm assembly pivotally supported on the frame for to-and-fro pivotal movement and including an armature positioned adjacent, and movable toward and away from, the other end portion of the core as the operating arm assembly pivots to-and-fro, said operating arm assembly further including spring-biased retaining means biasing the operating arm assembly so as to urge the armature away from the core and resiliently biasing the armature into engagement with one of said parallel surfaces, said retaining means including securing means resiliently biased into interengaging relationship with the other of said parallel surfaces, said retaining means, in cooperation with the frame, removably retaining the operating arm assembly in pivotal relationship with the frame and permitting removal of the entire operating arm assembly as a single integral unit from the frame without the use of tools, and contact means cooperating With the operating arm assembly for making and breaking circuits to be controlled by the relay.

2. A relay according to claim 1 wherein said contact means comprises at least one modular switching unit having contacts movable between open and closed positions by depression and release of a self-restoring reciprocable push button, said relay additionally including a supporting base and at least one mounting bracket, said mounting bracket being adapted to support either one or two of the switching units, selectively, in spaced relation to said base, and said base having means for mounting either one or two mounting brackets thereon, selectively, the push button of each switching unit being positioned in the path of to-and-fro movement of the operating arm assembly, whereby from one to four switching units may be mounted, selectively, for operation by said operating arm assembly.

3. A relay according to claim 1 wherein said contact means comprises a stationary contact assembly having a pair of stationary contacts, and said operating arm assembly carries a contact bridge cooperating with the stationary contacts for making and breaking a circuit through the stationary contacts as the operating arm. assembly pivots to-and-fro.

4. A relay according to claim 1 wherein said operating arm assembly includes an operating arm having means adapted for mounting, selectively, a contact bridge or an extension means on the operating arm, the contact bridge being so mounted when the relay is provided with contact means comprising a stationary contact assembly having a pair of stationary contacts, said contact bridge cooperating with the contact assembly for making and breaking a circuit through the stationary contacts as the operating arm assembly pivots to-and-fro, and the extension means being so mounted when the relay is provided with contact means comprising three or more modular switching units having self-contained contacts movable between open and closed circuit positions by depression and release of respective self-restoring reciprocable push buttons, said extension means cooperating with said switching units to reciprocate the push buttons as the operating arm assembly pivots toand-fro.

5. A relay according to claim 1 wherin the coil has a locating protrusion extending radially from the body of the coil, and said locating protrusion has a surface which cooperates with the frame to prevent rotation of the coil on the core.

6. A relay according to claim 1 wherein said coil is formed of helically wound strap material and has two terminal arm portions extending outwardly of the body of the coil, said means facilitating connection of said coil to a source of control power comprises a pair of identical terminal support members each having tab and slot portions, the tab and slot portions of one support member being mutually interengageable with the tab and slot portions of the other support member in two distinct positions of the support members with respect to each other, said terminal arm portions being connected to said support members, respectively, whereby said support members may be used with a coil having either of two different terminal arm configuration.

7. A realy according to claim 1 additionally including a base and wherein said magnetic frame has a second portion disposed genreally at right angles to the firstmentioned portion, and said frame and said core are secured with respect to each other and to the base by a screw which passes through aligned openings in the base and said second portion and is received in a threaded axial socket in the core.

8. A relay according to claim 1 additionally including a base which is generally vertical in the normal mode of use of the relay and wherein the base has a substantially flat central portion, said magnetic frame portion extends substantially normal to the flat portion of the base, said frame portion having an elongated groove formed on said one of said parallel surfaces and spaced from and extending generally parallel to the plane of the flat portion of the base, and said armature is generally flat and has a beveled edge portion received in the groove in knife-edge bearing relationship with respect to the frame.

9. A relay according to claim 8 wherein the other of said parallel surfaces is an upper surface of said frame portion.

10. A relay according to claim 9 wherein said securing means is carried by a shaft, the shaft passes through an open-ended slot in said frame portion, and the slot opens away from the base thereby to permit the operating arm assembly to be readily removed from the frame portion without the use of tools.

11. A relay according to claim 9 wherein the upper surface of said frame portion has relatively shallow notches formed therein, and said securing means has a seating portion which seats in said notches.

12. A relay according to claim 11 wherein said frame portion is elongated in a direction away from said base, and said notches are aligned with each other transversely of the frame portion and spaced longitudinally of the frame portion with respect to said groove.

13. A relay according to claim 11 wherein the securing means is carried by a shaft having a spring-retaining seat at one of its end portions and wherein the retaining means additionally includes a helical spring surrounding said shaft and seated at one of its ends on the spring-retaining seat so as to bias said shaft and said securing means in a ,direction so that said seating portions are seated in said notches with said armature in knife-edge bearing relationship with said frame.

14. A relay according to claim 13 wherein said shaft has a threaded portion opposite said one end portion and said securing means is threadedly received on the threaded portion of the shaft so as to permit adjustment of the securing means on the threaded portion of the shaft.

15. A relay according to claim 14 wherein said securing means includes a threaded portion in addition to said seating portion, said seating portion being captively rctained with respect to said threaded portion but free to rotate relative thereto, thereby to permit said adjustment of said securing means on the threaded portion of the shaft without disturbing the seating engagement of the seating portion with said frame.

16. A multipurpose clapper-type D-C relay comprising a magnetic frame, a flux-conductive core in flux-conducting relation at one of its end portions with the frame, a coil surrounding the core, means facilitating connection of the coil to a source of control power, a movable operating arm assembly pivotally supported on the frame for toand-fro pivotal movement and including an armature positioned adjacent, and movable toward and away from, the other end portion of the core as the operating arm assembly pivots to-and-fro, said operating arm assembly further including spring-biased retaining means biasing the operating arm assembly so as to urge the armature away from the core and resiliently biasing the operating arm assembly into engagement with the frame, said retaining means, in cooperation with the frame, removably retaining the operating arm assembly in pivotal relationship with the frame and permitting removal of the entire operating arm assembly as a single integral unit from the frame without the use of tools, and contact means cooperating with the operating arm assembly for making and breaking circuits to be controlled by the relay, said 10 contact means comprising at least one modular switching unit having contacts movable between open and closed positions by depression and release of a self-restoring reciprocable push button, said relay additionally includ- 5 ing a supporting base and at least one mounting bracket,

said mounting bracket being adapted to support either one or two of the switching units, selectively, in spaced relation to said base, and said base having means for mounting either one or two mounting brackets thereon,

l0 selectively, the push button of each switching unit being positioned in the path of to-and-fro movement of the operating arm assembly, whereby from one to four switching units may be mounted, selectively, for operation by said operating arm assembly.

5 HA'ROLD BROOME, Primary Examiner 

